Here's what I would try.
Let's say that the sample that is too big to fit in the graduated cylinder has a volume
By definition, the density of the mineral,
So for the initial sample, you have--I'll skip the units for simplicity
#rho = M/V" "" "color(darkorange)("(*)")#
Now, cut a piece of this sample that is small enough to fit in a graduated cylinder. Place this small piece on a scale and record its mass, let's say
Use the graduated cylinder to determine its volume.
Let's say that this small piece has a volume
Since the density of the mineral must be the same regardless of the mass of the sample and the volume it occupies, you can say that--I'll skip the units for simplicity
#rho = m/v#
You can now use equation
#M/V = m/v#
Rearrange to find
#M/V = m/v implies V = (Mcolor(red)(cancel(color(black)("g"))))/(mcolor(red)(cancel(color(black)("g")))) * vcolor(white)(.)"mL"#
#V = (M/m * v)color(white)(.)"mL"#
And there you have it, the volume of the initial sample as a function of its mass